Router Password

I have recently been getting nat restricted on my xbox whilst playing MW3 and i barely get any servers whilst playing BF3. I dont have any information about the router username or password, tried all the generic ones. I read another post where plusnet staff have said they would send the customer their router username and password and also read another post where the plusnet staff implied they had changed the router settings remotely to solve the Nat issue. Please help me resolve my restricted NAT issue!!!How do i fnd my router password aqnd username?Thanks!